According to the conventional synchronous control technique, a command is synchronously provided to the main shaft motor control device and the subsidiary shaft motor control device, respectively. Alternatively, a command is provided to the subsidiary shaft motor control device synchronously with the present position of the main shaft motor. Further, the present applicant proposed a synchronous control apparatus in which the predictive control is applied to the synchronous control as disclosed in Japanese Patent Application No. 6-288994. In the synchronous control apparatus described above, predictive control is conducted on the subsidiary shaft by a future position command of the subsidiary shaft obtained by predicting a future position of the main shaft.
However, according to the conventional synchronous control technique, it is difficult to conduct synchronous control with high accuracy because the dynamic characteristic of the main shaft is different from that of the subsidiary shaft. The art disclosed in Japanese Patent Application No. 6-288994 is proposed in order to solve the above problem and to enhance the synchronous accuracy. However, the following problems may be encountered hen the above device is used. In this device, when the future main shaft position is predicted, not the main shaft position command of the future but the main shaft position command at the present moment is used. Therefore, when the main shaft position command is changed, control can not be changed in quick response, and the synchronous accuracy is deteriorated.
According to the conventional synchronous control technique, when input of the position command into the main shaft control device and the subsidiary shaft control device is delayed or when detection of the main shaft position is delayed, the synchronous accuracy is deteriorated in accordance with the delay.
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide a synchronous control apparatus capable of realizing synchronous control, the control accuracy of which is higher than that of the conventional apparatus. Further, synchronous accuracy of this synchronous control apparatus is not deteriorated even if input of the position command is delayed and also detection of the main shaft position is delayed.